Descent with Modification Natural Selection – A population can change over time if individuals have heritable traits that leave more offspring than others Natural selection results in evolutionary adaptation – enhancing an organism’s survival and reproduction Evolution is biological change over time

The Historical Context for Evolutional Theory Charles Darwin’s book, The Origins of Species, rocked the world! –It challenged prevailing scientific views –It challenged a worldwide view that had been taught for centuries, such as The Earth is only a few thousand years old The Earth is populated by unchanging forms of life that has been individually made during the single week in which the Creator formed the entire universe.

Theories of Geologic Gradualism Study of fossils – in sedimentary rock, fossil species that are deeper in the stratum are more dissimilar from modern species Gradualism – profound change in the cumulative product of slow but continuous processes. –Darwin concluded Earth must be very old –Several slow and subtle processes can add up to substantial change

Early Theories of Evolution Jean Baptiste Lamarck –Theory of use and disuse – body parts that were used more grew bigger and stronger; those that were not would deteriorate. Ex. giraffe’s neck and fiddler crab’s claw –Inheritance of acquired characteristics – modifications and organism acquired during its life could be passed down to its offspring. Ex. with much use, the giraffe’s neck grows longer and this long neck is passed down to its offspring

Scientists who influenced Darwin Lyell Principles of Geology Plant and animal species emerged, developed variations and then became extinct

Scientists who influenced Darwin Malthus- populations outgrew their food supplies causing competition Essay on the Principle of Population (1798)

The Darwinian Revolution Charles Darwin (1809 – 1882) At age 16 Darwin went to medical school, but found it “boring and distasteful” In 1831, Darwin set sail around the world on the HMS Beagle as the ship’s naturalist

The Darwinian Revolution Darwin noted that animals living on the Galapagos Islands live nowhere else in the world – although they resemble those on South American’s mainland. –Origin of new species and adaptation to environment are closely related

The Darwinian Revolution By the 1840s, Darwin had already established his theories of natural selection In 1859, he published “The Origin of Species” –He did not use the word evolution → instead he used “descent with modification” –Evolution is an explanation for life’s unity and diversity –Natural selection is the cause of adaptive evolution –99% of all species that ever lived are extinct

The Darwinian Revolution Darwin’s Main Ideas Natural selection is differential success in reproduction –Tendency towards overproduction –Not all offspring survive (struggle for survival) –Variations exist and are inherited –Those best suited to their environment will live longer and leave more offspring –Favored traits disproportionately represented in the next generation – thus the population changes as a whole  Artificial selection supports these claims

Some Subtleties of Natural Selection Populations evolve, not individuals Heritable variations are amplified or diminished (must be a heritable variation) Situational – some adaptations may be advantageous in one environment and detrimental in another

More Examples of Natural Selection Evolution of insecticide resistance in hundreds of insect species Evolution of antibacterial resistance in bacteria species

Evidence for Evolution 1. Fossils 2. Comparative anatomy 3. Comparative embryology 4. Biochemistry 5. Genetic evidence 6. Direct evidence

Fossils FOSSILS mold or cast of organism left in rock, fossilized bone and teeth life becomes more complex over time record is incomplete

Evidence for Evolution RELATIVE DATING layers in rock bed used to date organisms

Evidence for Evolution PHYLOGENY- description of the lines of descent of organisms as they lived through history.

Other Evidence of Evolution HOMOLOGY – similarity in characteristics resulting from common ancestry 1.Anatomical –Homologous structures – have the same structure, but different functions –Vestigial organs – structures of marginal, if any, importance to the organism 2.Embryological –All animals have similar embryonic stages 3.Molecular –Comparing DNA and RNA to determine how related species are to another

Comparative Anatomy: Homologous structures

Vestigial Organs Vestigial Remains of a Pelvic Girdle in a Whale

Comparative Embryology the study of developing plants and animals Below is the pictures of embryos for a CHICKEN, FISH, HUMAN, RABBIT, and TORTOISE. Can you guess which one is each type of organism?

Comparative Embryology Comparative Embryology- The complete picture

Evidence for Evolution Genetic Evidence Mutations- mistakes in the genetic code –Causes changes in populations over time Population genetics- researchers use mathematical descriptions of genetic make ups to help them trace evolutionary trends within populations Selective Breeding- humans choose plants/animals with most desirable traits and breed them to pass those traits to offspring

Evidence for Evolution Direct Evidence Rapid Evolution –Strains of bacteria becoming resistant to antibiotics –Weeds and herbicides –Insects and insecticides

Biogeography The geographic distribution of a species Species tend to be more closely related to other species from the same area than to other species with the same way of life but living in different areas

Final words “Absence of evidence is not evidence of absence.” Charles Darwin